The manufacture of fructose containing syrup has been known for many years and, generally, such manufacture has been accomplished in two principal ways. In accordance with one way, a sucrose solution is hydrolyzed to prepare an invert sugar syrup. Another way is to treat dextrose with an isomerase enzyme or alkali so as to convert glucose to fructose by an enzyme or alkali isomerization process. Such processes, however, provide syrups usually containing less than about 50 percent fructose on a dry solids basis (d.s.b.). It is known to take these fructose containing syrups and increase the level of fructose by a chromatographic fractionation process. Such process is widely used in the industry to provide syrups containing 55 percent, or greater, fructose on a dry solids basis.
The chromatographic process for increasing the level of fructose provided by hydrolysis of sucrose or by isomerization of dextrose, involves the evaporation or concentration of a fructose containing syrup to a dry solids (d.s.) content of about 60 weight percent on a total weight basis. The syrup is subjected to a fractionation step, after dilution with water, in an absorption column which provides a raffinate which must be handled. The product must be carbon refined, and ion exchange refined, whereupon it is subjected to a final evaporation to a dry solids content of about 77 weight percent. The end product has about 55 percent or more fructose, d.s.b. However, this chromatographic process has certain disadvantages and it would be desirable to avoid the fractionation step and the final ion exchange refining step. Further, it would be desirable to avoid the production of raffinate and to minimize the microbiological problems associated with the chromatographic process. It would also be desirable to reduce the cost of the chromatographic process and to limit the energy requirements of such process.
A process for the manufacture of high fructose syrup is disclosed in U.S. Pat. No. 4,395,292 issued July 26, 1983. The process disclosed in this patent involves the use of a molecular exclusion column to remove dextrose and higher saccharides from the syrup. However, this process has the disadvantages which are attendant to the chromatographic process.
U.S. Pat. No. 3,704,168 issued Nov. 28, 1972 is directed to a process for the crystallization of glucose, fructose, or a mixture of glucose and fructose. The patent teaches the formation of a solution in which a mixed sugar is present containing glucose and fructose which is dissolved in a combination medium comprising a liquid polyhydric alcohol, and a liquid monohydric alcohol having a water content of less than 5 percent. The solution is held under supersaturated conditions and a seed crystal is added to effect crystallization. However, this process is costly and does not have the advantages of the present invention.
U.S. Pat. No. 4,371,402 issued Feb. 1, 1983 is directed to a process for preparation of fructose containing solid sugar from a fructose containing liquid sugar by the steps of dehydration, aging and solidification. The process disclosed involves using an azeotropic organic solvent and a dehydration step utilizing a stream of gas. The process is expensive and not of great advantage in the commercial production of high fructose containing syrups.
British Pat. No. 2,087,400 issued May 31, 1984, is directed to a process for the production of a syrup having a high fructose concentration. In accordance with the teachings of this application, a glucose syrup is mixed with a crystallization product containing dissolved fructose and glucose, as well as glucose crystals, to form a homogeneous solution. The solution is then isomerized and evaporated whereupon it is seeded with glucose crystals. The seeded mixture is cooled to crystallize glucose, which is recycled and mixed with the glucose syrup. However, this process does not provide good results in commercial practice.
It is a principal object of this invention to provide an improved process for enriching the fructose content of a fructose containing syrup.
A further object of the invention is to provide an improved method of manufacturing high fructose syrup having at least about 55 percent or more fructose d.s.b.
A still further object of this invention is the provision of a more efficient, lower cost manufacturing process for high fructose syrups.
Other objects and advantages of the invention will become apparent by reference to the following description.
Throughout the specification and claims all ratios and percentages are stated on a weight basis, temperatures are in degrees Celsius and pressures are in KPascals over (or under) ambient unless otherwise indicated.